Pushbutton telephone system

Abstract

A telephone connection is established between a pushbutton telephone set and one of telephone lines through a pushbutton telephone set unit, a speech highway, and a telephone line unit. When one of line and extension keys of the pushbutton telephone set is pressed by the user during the telephone connection, a CPU in a control unit determines whether the telephone connection is being made based on the period of time that has elapsed after the pushbutton telephone set has captured the telephone line. If the telephone connection is being made as determined by the CPU, then the CPU controls a time switch circuit according to hold function data stored in a RAM to connect the telephone line unit to a hold tone generator through the speech highway, thus holding the telephone connection. Thereafter, the CPU captures a telephone line corresponding to the depressed one of the line and extension keys.

What is claimed is: 
     
       1. A pushbutton telephone system comprising: a plurality of telephone lines and an extension line;   at least one pushbutton telephone set connected to said telephone lines and said extension line and having a plurality of line keys associated with said telephone lines, respectively, and an extension key associated with said extension line;   timer means for measuring a period of time which elapses after said pushbutton telephone set captures one of the telephone lines until one of said line keys or said extension key is pressed;   decision means for determining whether one of said telephone lines is carrying a call when one of said line keys or said extension key is pressed, by determining whether the period of time which is measured by said timer means is longer than a preset period of time;   holding means for holding said one of the telephone lines which is carrying a call when said one of said line keys or said extension key is pressed if said one of the telephone lines is determined as carrying a call by said decision means; and   control means for controlling said pushbutton telephone set to capture one of said telephone lines or said extension line which corresponds to the pressed one of said line keys or said extension key when said one of the telephone lines which is carrying a call is held by said holding means.   
     
     
       2. A pushbutton telephone system according to claim 1, wherein said holding means comprises means for holding said one of the telephone lines which is carrying a call for 2 seconds. 
     
     
       3. A pushbutton telephone system according to claim 1, further comprising setting means for setting and modifying a period of time for which said one of the telephone lines which is carrying a call is held by said holding means. 
     
     
       4. A pushbutton telephone system according to claim 1, further comprising indicating means for sending a signal indicating the setting of a hold function to hold said one of the telephone lines which is carrying a call with said holding means to said pushbutton telephone set when said decision means is activated and sending a signal indicating a disabling of said hold function to said pushbutton telephone set when said preset period of time elapses. 
     
     
       5. A pushbutton telephone system according to claim 1, further comprising synthetic speech supply means for supplying a synthetic speech signal indicating the setting of a hold function to hold said one of the telephone lines which is carrying a call with said holding means to said pushbutton telephone set when said decision means starts to determine whether said one of the telephone lines is carrying a call based on said period of time. 
     
     
       6. A pushbutton telephone system according to claim 5, wherein said pushbutton telephone set has audio output means for producing a sound represented by said synthetic speech signal which is supplied to said pushbutton telephone set. 
     
     
       7. A pushbutton telephone system according to claim 4, wherein said pushbutton telephone set has visual display means for displaying visual information represented by said signal indicating the setting of a hold function. 
     
     
       8. A pushbutton telephone system according to claim 7, wherein said visual display means comprises means for displaying the visual information as letters. 
     
     
       9. A pushbutton telephone system according to claim 7, wherein said visual display means comprises light-emitting means for emitting light as said visual information. 
     
     
       10. A pushbutton telephone system according to claim 9, wherein said light-emitting means comprises means for emitting flickering light as said visual information. 
     
     
       11. A pushbutton telephone system according to claim 9, wherein said light-emitting means comprises two-color light-emitting means for alternately and intermittently turning on two color signals. 
     
     
       12. A pushbutton telephone system according to claim 4, wherein said pushbutton telephone set has buzzer means for producing a buzzer sound represented by said signal indicating the setting of a hold function. 
     
     
       13. A pushbutton telephone system according to claim 12, wherein said buzzer means comprises means for producing an intermittent buzzer sound represented by said signal indicating the setting of a hold function. 
     
     
       14. A pushbutton telephone system according to claim 9, wherein said light-emitting means comprises a plurality of light-emitting elements positioned in said line keys, respectively. 
     
     
       15. A pushbutton telephone system according to claim 9, wherein said light-emitting means comprises a plurality of light-emitting elements positioned near said line keys, respectively. 
     
     
       16. A pushbutton telephone system according to claim 3, further comprising telephone number detecting means for detecting a telephone number signal representing a telephone number which is dialed by said pushbutton telephone set during said period of time set by said setting means, and indicating means for sending a signal indicating the disabling of said hold function to said pushbutton telephone set when a telephone number signal is detected by said telephone number detecting means. 
     
     
       17. A pushbutton telephone system according to claim 16, wherein said pushbutton telephone set has visual display means for displaying visual information represented by said signal indicating the setting of a hold function, further comprising means for de-energizing said visual display means when said signal indicating the disabling of said hold function is sent from said indicating means to said pushbutton telephone set. 
     
     
       18. A pushbutton telephone system according to claim 16, further comprising synthetic speech supply means for supplying a synthetic speech signal indicating the setting of a hold function to hold said one of the telephone lines which is carrying a call with said holding means to said pushbutton telephone set when said decision means starts to determine whether said one of the telephone lines is carrying a call based on said period of time, and means for deenergizing said synthetic speech supply means when said signal indicating the disabling of said hold function is sent from said indicating means to said pushbutton telephone set. 
     
     
       19. A pushbutton telephone system according to claim 16, wherein said pushbutton telephone set has light-emitting means for emitting light as said signal indicating the setting of a hold function, further comprising means for de-energizing said light-emitting means when said signal indicating the disabling of said hold function is sent from said indicating means to said pushbutton telephone set. 
     
     
       20. A pushbutton telephone system according to claim 16, wherein said pushbutton telephone set has buzzer means for producing a buzzer sound represented by said signal indicating the setting of a hold function, further comprising means for de-energizing said buzzer means when said signal indicating the disabling of said hold function is sent from said indicating means to said pushbutton telephone set. 
     
     
       21. A pushbutton telephone system according to claim 3, further comprising busy tone detecting means for detecting a busy tone signal from one of said telephone lines which corresponds to one of said line keys that is pressed during said period of time set by said setting means, and indicating means for sending a signal indicating the disabling of said hold function to said pushbutton telephone set when a busy tone signal is detected by said busy tone detecting means. 
     
     
       22. A pushbutton telephone system according to claim 21, wherein said pushbutton telephone set has visual display means for displaying visual information represented by said signal indicating the setting of a hold function, further comprising means for de-energizing said visual display means when said signal indicating the disabling of said hold function is sent from said indicating means to said pushbutton telephone set. 
     
     
       23. A pushbutton telephone system according to claim 21, further comprising synthetic speech supply means for supplying a synthetic speech signal indicating the setting of a hold function to hold said one of the telephone lines which is carrying a call with said holding means to said pushbutton telephone set when said decision means starts to determine whether said one of the telephone lines is carrying a call based on said period of time, and means for deenergizing said synthetic speech supply means when said signal indicating the disabling of said hold function is sent from said indicating means to said pushbutton telephone set. 
     
     
       24. A pushbutton telephone system according to claim 21, wherein said pushbutton telephone set has light-emitting means for emitting light as said signal indicating the setting of a hold function, further comprising means for de-energizing said light-emitting means when said signal indicating the disabling of said hold function is sent from said indicating means to said pushbutton telephone set. 
     
     
       25. A pushbutton telephone system according to claim 21, wherein said pushbutton telephone set has buzzer means for producing a buzzer sound represented by said signal indicating the setting of a hold function, further comprising means for de-energizing said buzzer means when said signal indicating the disabling of said hold function is sent from said indicating means to said pushbutton telephone set.